Process for producing a halobenzene

ABSTRACT

A process for producing a halobenzene represented by the formula: ##STR1## where R is a lower alkyl group, a lower alkoxy group or a halogen atom, and X is a halogen atom, which comprises halogenating a benzene represented by the formula: ##STR2## where R is as defined above, in a liquid phase in the presence of a catalyst, characterized in that the catalyst is a combination of an aliphatic carboxylic acid component and a zeolite having a SiO 2  /Al 2  O 3  molar ratio of from 3 to 8 and a pore size of from 6 to 10 Å.

This is a continuation of Ser. No. 057,650, filed June 9, 1987, now U.S.Pat. No. 4,831,199.

The present invention relates to a process for producing a halobenzenesuch as chlorotoluene or dichlorobenzene which is useful as a startingmaterial for the production of medicines and agricultural chemicals.More particularly, it relates to a process for producing a p-halobenzenewith high selectivity by halogenating a benzene with use of a novelcatalyst.

Halobenzenes are useful as starting materials for medicines andagricultural chemicals. Particularly, there are strong demands forp-halobenzenes among them. Accordingly, there have been various studiesto improve the selectivity for p-halogenation.

As a process for the liquid phase halogenation of an alkyl benzene, ithas been common to conduct the halogenation in the presence of a Lewisacid catalyst such as antimony chloride, ferric chloride or aluminumchloride by means of a halogenating agent such as chlorine gas. However,such a process produces an o-chloroalkylbenzene as a major product and am-chloro derivative and a polychloro derivative as by-products, wherebyit is impossible to produce a p-chloroalkyl-benzene in good selectivityas high as at least 40%. Under the circumstances, there have beenvarious researches for the developments of catalysts to improve theselectivity for a p-chloroalkylbenzene, and there have been someproposals.

For example, there have been known a method wherein a p-chloroderivative is obtained in a selectivity of from 45 to 52% by means of acatalyst composed of a Lewis acid and sulfur or selenium, a methodwherein a p-chloro derivative is obtained in a selectivity of from 55 to60% by means of a catalyst composed of a Lewis acid and thianthrene(U.S. Pat. No. 4,031,147), and a method wherein a p-chloro derivative isobtained in a selectivity of from 52 to 60% by means of a catalystsystem composed of a Lewis acid and a phenoxthine compound (U.S. Pat.No. 4,444,983). On the other hand, with respect to chlorination ofchlorobenzene, there have been known a method wherein p-dichlorobenzeneis obtained in a selectivity of from 60 to 70% by reacting chlorobenzenewith chlorine in the presence of an iron sulfide catalyst (GB No.1,476,398), and a method wherein a p-dichlorobenzene is obtained in aselectivity of 72% by reacting chlorobenzene with chlorine by means ofselenium or a selenium compound as a catalyst (Japanese Examined PatentPublication No. 34010/1975).

However, these conventional methods are not necessarily satisfactory asa process for the production of a p-halobenzene, because the selectivityfor the p-halo derivative is low in each case.

Accordingly, it is an object of the present invention to provide aprocess for producing a p-halobenzene in high selectivity by a liquidphase halogenation of a benzene in the presence of a catalyst.

It has been found that the object of the present invention can beattained by using as the catalyst a combination of an aliphaticcarboxylic acid component and a certain zeolite. The present inventionis based on this discovery.

Namely, the present invention provides a process for producing ahalobenzene represented by the formula: ##STR3## where R is a loweralkyl group, a lower alkoxy group or a halogen atom, and X is a halogenatom, which comprises halogenating a benzene represented by the formula:##STR4## where R is as defined above, in a liquid phase in the presenceof a catalyst, characterized in that the catalyst is a combination of analiphatic carboxylic acid component and a zeolite having a SiO₂ /Al₂ O₃molar ratio of from 3 to 8 and a pore size of from 6 to 10 Å.

Now, the present invention will be described in detail with reference tothe preferred embodiments.

As the substituents R in the starting compound of the formula II used inthe process of the present invention, there may be mentioned a straightchained or branched alkyl or alkoxy group, or a halogen atom such as afluorine atom, a chlorine atom or an bromine atom. Particularlypreferred is an alkyl group having from 1 to 4 carbon atoms or achlorine atom.

In the process of the present invention, it is essential to use as thecatalyst a combination of an aliphatic carboxylic acid component and azeolite having a SiO₂ /Al₂ O₃ molar ratio of from 3 to 8 and a pore sizeof from 6 to 10 Å. When a zeolite with a SiO₂ /Al₂ O₃ molar ratio or apore size being outside the above-mentioned range, is used, theselectivity for a p-halobenzene will be substantially poor.

A typical representative of the zeolite which satisfies the aboveconditions, is L-type zeolite, which is a crystalline aluminosilicatehaving a SiO₂ /Al₂ O₃ molar ratio of from 4 to 8 and a pore size of fromabout 7 to about 10 Å. As another example of the zeolite which satisfiesthe above conditions, there may be mentioned Y-type zeolite having aSiO₂ /Al₂ O₃ molar ratio of from 3 to 7 and a pore size of from about 6to about 9 Å.

For the catalyst of the present invention, it is also possible to employa synthetic zeolite or natural zeolite having the same X-ray diffractionspectrum as the above-mentioned L-type or Y-type zeolite. Further, theion exchangeable cations contained in such zeolite are usually sodium orpotassium, but may further include other cations. As such cations, theremay be mentioned metal ions or protons belonging to Group IA, Group IIA,Group IIIA, Group IVA or Group VA of the periodic table. These cationsmay be of the same type or of two or more different types.

For the purpose of the present invention, the term "aliphatic carboxylicacid component" includes an aliphatic carboxylic acid and itsderivatives such as a halide, anhydride or metal salt of an aliphaticcarboxylic acid. As the aliphatic carboxylic acid, there may bementioned acetic acid, propionic acid, isovaleric acid, monochloroaceticacid, monobromoacetic acid, dichloroacetic acid, trichloroacetic acid,α-chloropropionic acid, β-chloropropionic acid, difluoroacetic acid,trifluoroacetic acid, pentafluoropropionic acid orβ-chloro-tetrafluoropropionic acid which may be substituted orunsubstituted. The metal salt may be a sodium, potassium or barium saltof an aliphatic carboxylic acid. The halide may be a chloride or abromide of an aliphatic carboxylic acid. Among them, aliphaticcarboxylic acids and their metal salts are preferred. Among them, sodiumsalts or potassium salts are further preferred. Further, aliphaticcarboxylic acids and their metal salts may be employed in, the form ofhydrates.

The aliphatic carboxylic acid component is used in an amount of at least1% by weight relative to the zeolite. However, from the industrial pointof view, it is preferred to use the aliphatic carboxylic acid componentin an amount within a range of from 3 to 30% by weight relative to thezeolite.

In the present invention, the zeolite and the aliphatic carboxylic acidcomponent may be combined prior to the halogenation reaction.Alternatively, the zeolite and the aliphatic carboxylic acid componentmay simultaneously be added to the reaction system at the time of thehalogenation.

The premixing may be conducted in such a manner that the zeolite issuspended in a solvent, a predetermined amount of the aliphaticcarboxylic acid component is added thereto, then, the solvent isdistilled off and the mixture is dried under reduced pressure.

On the other hand, in the case of combining them at the time of thereaction, the zeolite is suspended in the starting material benzene fedin the halogenation reactor, then a predetermined amount of thealiphatic carboxylic acid component is added thereto, and the mixture isstirred at a temperature lower than the boiling point, preferably from20° to 100° C., followed by the subsequent halogenation.

The combination of the zeolite and the aliphatic carboxylic acidcomponent can be adequately conducted by one of the above methods.However, if desired, both methods may be employed for the adequatetreatment of the zeolite with the aliphatic carboxylic acid component.

To conduct the halogenation of a benzene in accordance with the processof the present invention, for instance, the zeolite treated with thealiphatic carboxylic acid component is added in an amount of at least0.01 g, preferably from 0.1 to 10 g, per mol of the starting materialbenzene, and a halogenating agent is introduced into the mixture in aliquid phase while stirring the mixture at a temperature of not higherthan the boiling point. In this operation, a reaction solvent may beemployed as the case requires. As the halogenating agent, there may beemployed any agent commonly employed for the halogenation of aromaticrings. Preferred are chlorine, bromine and sulfuryl chloride. Thesehalogenating agents may be employed as diluted with an inert gas such asnitrogen. The reaction temperature for the halogenation is usually from0° C. to the boiling point of the reaction mixture, preferably from 20°to 100° C. from the practical viewpoint. The reaction may be conductedunder reduced or elevated pressure, but is usually conducted underatmospheric pressure.

According to the process of the present invention, it is possible toselectively and efficiently halogenate the p-position of the benzene ofthe formula II while suppressing the halogenation at the o-position, andto minimize the formation of by-products such as side chain-halogenatedproducts or polyhalogenated products, whereby a highly usefulp-halobenzene of the formula I can be obtained in good selectivity.

Further, according to the process of the present invention, in a casewhere a p-dihalobenzene is to be produced from a monohalobenzene as thestarting material, it is possible to advantageously conduct theproduction of the monohalobenzene from benzene and the step ofhalogenating the monohalobenzene to the p-dihalobenzene, continuously inthe same reactor.

Furthermore, according to the process of the present invention, theoperation of the reaction and the subsequent after-treatment is simple,and the catalyst can be reused. Thus, the process of the presentinvention is suitable as an industrial process for the production ofp-halobenzenes.

Now, the present invention will be described in further detail withreference to Examples. However, it should be understood that the presentinvention is by no means restricted by these specific Examples.

EXAMPLE 1

Into a 200 ml reaction flask equipped with a condenser, a thermometer, astirrer and a gas supply tube, 5 g of L-type zeolite (tradename:TSZ-506, manufactured by Toyo Soda Manufacturing Co., Ltd.) and 92.1 g(1 mol) of toluene were introduced, and 1.0 g of monochloroacetic acidwas added thereto. The mixture was maintained at 70° C., and stirred for30 minutes while supplying nitrogen gas. Then, chlorine gas was suppliedat a rate of 0.25 mol/hr for 4 hours to conduct the reaction whilemaintaining the reaction temperature at 70° C. After the completion ofthe reaction, the reaction product thereby obtained, was analyzed by gaschromatography, whereby it was found that the conversion of toluene was98.3%, the production ratio of o-chlorotoluene/p-chlorotoluene(hereinafter referred to simply as "o/p ratio") was 0.262, and theselectivity of p-chlorotoluene was 74.2%.

EXAMPLE 2

The reaction was conducted in the same manner as in Example 1 exceptthat monochloroacetic acid was added in an amount of 0.25 g, whereby theconversion of toluene was 95.3% and the o/p ratio was 0.269.

EXAMPLES 3 to 13 and COMPARATIVE EXAMPLES 1 and 2

The halogenation was conducted in the same manner as in Example 1 exceptthat a various substituted or unsubstituted aliphatic carboxylic acid asidentified in Table 1 was used instead of monochloroacetic acid, and thetemperature for the treatment of the zeolite and the reactiontemperature were adjusted to 50° C., 70° C. or 90° C. The results areshown in Table 1.

Further, for the purpose of comparison, the Table includes the resultsobtained from the cases wherein L-type zeolite as catalyst, and acombination of L-type zeolite with benzoic acid were employed.

                  TABLE 1                                                         ______________________________________                                                                Zeolite                                                                       treating                                                                      temp. &                                                                       reaction Conver-                                              Aliphatic carboxylic                                                                          temp.    sion   o/p                                   Example acid            (°C.)                                                                           (%)    ratio                                 ______________________________________                                        3       Acetic acid     70       99.8   0.319                                 4       α-Chloropropionic acid                                                                  70       93.8   0.233                                 5       β-Chloropropionic acid                                                                   70       90.4   0.220                                 6       β-Chloropropionic acid                                                                   90       92.0   0.325                                 7       Dichloroacetic acid                                                                           70       96.2   0.250                                 8       Difluoroacetic acid                                                                           70       99.4   0.250                                 9       Trifluoroacetic acid                                                                          70       99.7   0.344                                 10      Propionic acid  50       90.6   0.254                                 11      Monobromoacetic acid                                                                          50       99.4   0.248                                 12      Monochlorodifluoro-                                                                           50       99.8   0.248                                         acetic acid                                                           13      Pentafluoropropionic                                                                          50       99.8   0.296                                         acid                                                                  Compara-                                                                              None            70       95.1   0.496                                 tive 1                                                                        Compara-                                                                              Benzoic acid    70       93.9   0.608                                 tive 2                                                                        ______________________________________                                    

EXAMPLE 14

The halogenation was conducted in the same manner as in Example 1 exceptthat 112.6 g (1 mol) of chlorobenzene was used as the starting materialinstead of toluene, dichloroacetic acid was used instead ofmonochloroacetic acid, and the reaction time was changed to 5 hours,whereby the conversion of chlorobenzene was 90.5%, the production ratioof o-dichlorobenzene/p-dichlorobenzene was 0.071, and the selectivity ofp-dichlorobenzene was 92.7%.

EXAMPLE 15

The halogenation was conducted in the same manner as in Example 1 exceptthat Y-type zeolite (tradename: LZ-Y82, manufactured by Union CarbideCorp., U.S.A.) was used instead of L-type zeolite, 108.1 g (1 mol) ofanisole was used as the starting material instead of toluene, anddifluoroacetic acid was used instead of monochloroacetic acid, wherebythe conversion of anisole was 91.5%, and the production ratio ofo-chloroanisole/p-chloroanisole was 0.218.

EXAMPLE 16

After the completion of the reaction in Example 1, the catalyst wasrecovered from the reaction mixture. By using the recovered catalyst,the halogenation was repeated 4 times in the same manner as in Example1, whereby the reaction proceeded normally in each case and theconversion was 98.1% and the o/p ratio was 0.267.

EXAMPLE 17

Into a 200 ml reaction flask equipped with a condenser, thermometer, astirrer and a gas supply tube, 5 g of L-type zeolite (tradename:TSZ-506, manufactured by Toyo Soda Manufacturing Co., Ltd.) and 92.1 g(1 mol) of toluene were introduced, and 1.0 g of potassiumdichloroacetate was added thereto. The mixture was maintained at 50° C.and stirred for 30 minutes while supplying nitrogen gas. Then, chlorinegas was supplied at a rate of 0.25 mol/hr for 4 hours to conduct thereaction while maintaining the reaction temperature at 50° C. After thecompletion of the reaction, the reaction product thereby obtained, wasanalyzed by gas chromatography, whereby it was found that the conversionof toluene was 96.6%, the o/p ratio was 0.208, and the selectivity ofp-chlorotoluene was 79.63%.

EXAMPLES 18 to 22

The halogenation was conducted at 50° C. in the same manner as inExample 17 except that a various metal salt of a substituted orunsubstituted aliphatic carboxylic acid, as identified in Table 2, wasused instead of potassium dichloroacetate. The results are shown inTable 2.

                  TABLE 2                                                         ______________________________________                                                Metal salt of an aliphatic                                                                       Conver-  o/p                                       No.     carboxylic acid    sion (%) ratio                                     ______________________________________                                        18      Potassium acetate  89.9     0.313                                     19      Sodium dichloroacetate                                                                           99.2     0.259                                     20      Potassium difluoroacetate                                                                        90.4     0.292                                     21      Barium acetate     91.9     0.322                                     22      Sodium acetate (trihydrate)                                                                      87.7     0.363                                     ______________________________________                                    

EXAMPLE 23

The halogenation was conducted in the same manner as in Example 17except that 112.6 g (1 mol) of chlorobenzene was used as the startingmaterial instead of toluene, and the reaction temperature was changed to70° C., whereby the conversion of chlorobenzene was 90.5%, theproduction ratio of o-dichlorobenzene/p-dichlorobenzene was 0.062, andthe selectivity of p-dichlorobenzene was 93.4%.

EXAMPLE 24

After the completion of the reaction in Example 23, the catalyst wasrecovered from the reaction mixture. By using the recovered catalyst,the operation was repeated 4 times in the same manner as in Example 23,whereby the reaction proceeded normally and the conversion was 90.1% andthe production ratio of o-dichlorobenzene/p-dichlorobenzene was 0.075.

EXAMPLE 25

Into a 200 ml reaction flask equipped with a condenser, a thermometer, astirrer and a gas supply tube, 5 g of L-type zeolite (tradename:TSZ-504, manufactured by Toyo Soda Manufacturing Co., Ltd.) and 92.1 g(1 mol) of toluene were introduced, and 0.5 g of chloroacetyl chloridewas added thereto. The mixture was maintained at 50° C. and stirred for30 minutes while supplying nitrogen gas. Then, chlorine gas was,supplied at a rate of 0.25 mol/hr for 4 hours to conduct the reactionwhile maintaining the reaction at 50° C. After the completion of thereaction, the reaction product thereby obtained was analyzed by gaschromatography, whereby the conversion of toluene was 98%, the o/p ratiowas 0.312, and the selectivity of p-chlorotoluene was 70.38%.

EXAMPLE 26

The reaction was conducted in the same manner as in Example 25 exceptthat chloroacetyl chloride was added in an amount of 0.25 g, whereby theconversion of toluene was 90.1% and the o/p ratio was 0.338.

EXAMPLES 27 to 32

The halogenation was conducted at 70° C. in the same manner as Example25 except that a various benzene as identified in Table 3 was used asthe starting material instead of toluene. The results are shown in Table3.

                  TABLE 3                                                         ______________________________________                                        No.     The benzene (II)                                                                            Conversion (%)                                                                            o/p ratio                                   ______________________________________                                        27      Ethylbenzene  99.6        0.160                                       28      Cumene        94.6        0.108                                       29      t-Butylbenzene                                                                              95.9        0.036                                       30      Chlorobenzene 94.8        0.076                                       31      Anisole       89.0        0.192                                       32      Fluorobenzene 95.3        0.019                                       ______________________________________                                    

EXAMPLES 33 to 39

The halogenation was conducted at 70° C. in the same manner as inExample 25 except that a various aliphatic carboxylic acid halide oranhydride as identified in Table 4 was used instead of chloroacetylchloride used in Example 25. The results are shown in Table 4.

For the purpose of comparison, the table includes the results obtainedby using a combination of L-type zeolite with benzoyl chloride(Comparative Example 3).

                  TABLE 4                                                         ______________________________________                                               Aliphatic carboxylic                                                                            Conver-  o/p                                         No.    acid derivative   sion (%) ratio                                       ______________________________________                                        33     Trifluoroacetic anhydride                                                                       97.4     0.442                                       34     Acetic anhydride  86.3     0.409                                       35     Acetyl chloride   89.8     0.452                                       36     Chloroacetyl chloride                                                                           96.0     0.360                                       37     Dichloroacetyl chloride                                                                         85.2     0.438                                       38     Bromoacetyl chloride                                                                            82.3     0.442                                       39     Bromoacetyl bromide                                                                             79.7     0.437                                       Compara-                                                                             Benzoyl chloride  86.0     0.696                                       tive                                                                          Example 3                                                                     ______________________________________                                    

EXAMPLE 40

The halogenation was conducted at 70° C. in the same manner as inExample 25 except that 35.2 g (1.0 mol) of sulfuryl chloride wasdropwise added over a period of 4 hours instead of chlorine gas, andaging was conducted for 3 hours, whereby the conversion of toluene was99.4% and the o/p ratio was 0.293.

EXAMPLE 41

After the completion of the reaction in Example 25, the catalyst wasrecovered from the reaction mixture. By using the recovered catalyst,the operation was repeated in the same manner as in Example 25, wherebythe reaction proceeded normally, and the conversion was 98.2% and theo/p ratio was 0.320.

We claim:
 1. A process for producing a halobenzene of the formula:##STR5## wherein R is a lower alkyl group, a lower alkoxy group, or ahalogen atom selected from the group consisting of a fluorine atom, achlorine atom and a bromine atom, and X is a halogen atom selected fromthe group consisting of a fluorine atom, a chlorine atom, and a bromineatom, said process comprising halogenating, with a halogenating agentwhich is selected from the group consisting of chlorine, bromine andsulfuryl chloride, at a temperature and pressure suitable forhalogenating, a benzene compound of the formula: ##STR6## in a liquidphase in the presence of a catalyst, wherein said catalyst is acombination of a component selected from the group consisting of acidic,propionic acid, isovoleric acid, monochloroacidic acid, monobromoacidicacid, dichloroacidic acid, trichloroacidic acid, α-chloropropionic acid,β-chloropropionic acid, difluoroacidic acid, trifluoroacidic acid,pentafluoropropionic acid, β-chlorotetrafluoropropionic acid, sodium,potassium and barrium salts thereof, and a zeolite having a Si O₂ /Al₂O₃ molar ratio of from 3 to 8 and a pore size of from 6 to Å.
 2. Theprocess of claim 1, wherein said component is potassium dichloroacetate,sodium dichloroacetate, or potassium difluoroacetate.
 3. The process ofclaim 1, wherein said component is chloroacetylchloride.
 4. The processof claim 1, wherein said zeolite is used in an amount of at least 0.01gram per mole of said benzene compound of formula (II).
 5. The processof claim 1, wherein said zeolite is used in an amount of from 0.1 to 10grams per mole of said benzene formula (II).
 6. The process of claim 1,wherein said component is used in amount of at least 1% by weightrelative to said zeolite.
 7. The process of claim 1, wherein saidcomponent is used in amounts of from 3 to 30% by weight relative to saidzeolite.
 8. The process of claim 1, wherein said halogenating is carriedout at a temperature of from 0° C. to the boiling point of the reactionmixture.
 9. The process of claim 1, wherein said halogenating is carriedout at a temperature of from 20° C. to 100° C.
 10. The process of claim1, wherein R is a C₁₋₄ alkyl group or a chlorine atom.
 11. The processof claim 1, wherein said benzene compound of formula (II) is toluene.12. The process of claim 1, wherein said benzene compound of formula(II) is chlorobenzene.
 13. The process of claim 1, wherein said zeoliteis a L-type zeolite.